876. 链表的中间结点

Posted 2022-08-11 wuyi_all_in

 

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 快慢指针都在head开始，快指针为空时则是链表个数为偶数，慢指针为空时则是链表个数为奇数，

/**
 * Definition for singly-linked list.
 * struct ListNode 
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) 
 * ;
 */
class Solution 
public:
    ListNode* middleNode(ListNode* head) 
        ListNode *left=head;
        ListNode *right=head;
        //right->next,必须先判断right是否为空
        while(right!=NULL&&right->next!=NULL)
        
            //快慢指针
            right=right->next->next;
            left=left->next;
            
        
        return left;
        

    
;